When an automobile is subjected to a front impact, the driver of the automobile will continue moving forward relative to the vehicle due to inertial forces. This forward movement can cause the driver to collide with a rearward moving automobile steering system thus potentially injuring the driver. Collapsible steering columns are safety devices that have been utilized to stop the automobiles driver's forward momentum and minimize driver injury. Collapsible steering columns typically slow the driver's movement by collapsing to absorb energy from the driver when impacted by the driver. So that steering columns collapse under loads from the driver, external forces or influences acting on the steering columns should be considered when designing collapsible steering columns.
I-shafts are one major component which can influence a steering column's ability to resist a collapse. I-shafts transfer steering inputs (e.g., steering wheel rotations) from the steering column to the steering gear in automobile steering systems. As such, I-shafts are generally coupled to the steering column and steering gear. During a front-end impact, the steering gear, and therefore the I-shaft, both usually move rearward towards the steering column and driver. The I-shaft rearward force directed toward the steering column needs to be minimized, eliminated, and/or controlled so the steering column can be allowed to collapse forward and effectively absorb energy from a forward moving automobile driver.
One method to affect the I-shaft forces on the steering column includes using an I-shaft decoupler. Typically, an I-shaft decoupler enables an I-shaft to separate into two parts when a predetermined rearward force is exerted on the I-shaft. Thus, decoupling the steering column from the I-shaft enables the steering wheel and steering column to move forward with a driver due to the inertial forces exerted on a driver during front impact events. In theory, although this decoupling would seem to limit the maximum load an I-shaft transfers to a steering column, such is not the case.
While current steering column and I-shaft decoupling systems reduce the rearward force exerted on a driver in a front impact, these systems have several drawbacks. Current decoupling systems do not adequately control the two separated parts of the I-shaft ensuring that they do not adversely affect collapse of the steering column. For example, after decoupling an I-shaft, a lower part of the I-shaft could continue to move rearward and strike the steering column. In addition, the upper part of the I-shaft could contact a surrounding component such as the dash panel, becoming lodged in the dash panel, and strike the brake pedal assembly while the column is trying to collapse due to loads from the driver. These adverse affects can cause harm to automobile drivers because the steering column is not enabled to fully collapse, thus exerting extreme rearward forces on an automobile driver during a front-end collision. Additional drawbacks associated with current steering column and I-shaft decoupling systems include that current systems do not utilize the rearward force of the I-shaft to assist in completely collapsing the steering column, and current systems have a tendency to exert forces on drivers that exceed the force limits established by federal motor vehicle safety standards.